1. Field of the Invention
This invention relates to an image forming apparatus such as photocopier, printer, or the like and, more particularly, to an image forming apparatus in which sheets on which images are formed at an image forming section are conveyed with a directional change to a Ring section.
2. Description of Prior Art
In a printer, as an example of an image forming apparatus, some recently feature high printing quality of photographic tone, and to create a high class feeling of photography from printing paper, such a printer frequently uses, as a printing medium serving as a sheet to which images are printed, thick paper based materials like printing paper, or film based materials other than paper.
Various techniques producing images to print on those printing media have been known, and as indicated in JP-A-8-2090 (JP-A- is an abbreviation of xe2x80x9cJapanese Unexamined Patent Publicationxe2x80x9d) and JP-A-10-291306, a method has been known to obtain a high quality printing of a photographic tone by using a printing medium requiring a thermal processing and by applying the thermal processing at a fixing section to this printing medium after making printing at a printing section.
FIG. 18 is a diagram showing a printing section and a fixing section of a conventional printer. In this printer, a recording medium S requiring a thermal fixing processing after printing is introduced to a fixing section 102 upon changing the conveyance direction at a conveyance route 104 after printing is made at a printing section 101.
Because the recording medium S requiring a thermal fixing processing is rigid, printing may be disrupted in a case that the printing force from a fixing roller 103 formed at the fixing section 102 affects the conveyance of the recording medium S, where the recording medium S is introduced in the fixing section 102, and where a front end of the recording medium S is made to enter in the fixing section 102 while the printing is made on the recording medium S. Moreover, where the recording medium S passes through a conveyance route having a small curvature, the route affects the conveyance of the recording medium S, thereby disrupting the printing, and in the worst situation, preventing the recording medium from being conveyed.
To solve such disadvantages, one apparatus has been known, e.g., as shown in FIG. 19, having a conveyance route 106 in which the recording medium is not introduced into the fixing section 102 until printing is finished and whose radius of curvature is designed relatively large. In FIG. 19, numeral 105 is a conveyance roller pair. The conveyance roller pair 105 disengages the contact between the two rollers 105a, 105b so that the conveyance of the recording medium is not affected from the nipping force during printing. Numeral 107 is a reverse portion formed on a downstream side of the conveyance route 106 having a large radius of curvature. A reverse roller 108 is provided at the reverse portion 107 for reversing the recording medium.
With the printer thus structured, the recording medium is sent in a direction for the fixing section 102 by reversing the rotational direction of the reverse roller 108 right before the rear end of the recording medium is disengaged from the reverse roller 108.
Such a conventional printer can convey relatively rigid recording media without affecting the printing operation, but the printer apparatus body becomes large because the printer requires the conveyance route 106 having a large radius of curvature. When a conveyance route having such a large radius of curvature is formed, the conveyance route becomes longer, thereby lowering the throughput. On the other hand, if the apparatus body is made compact to solve those problems, the behaviors of the recording medium during fixing may cause to disturb the printing operation on the subsequent recording media.
With the view to improve those current circumstances, it is an object of the invention to provide an image forming apparatus in which apparatus size can be made compact and in which the throughput can be improved.
A representative structure according to the invention to solve the above problems is to provide a recording medium conveying apparatus for conveying a recording medium from one position to another position, the recording medium conveying including a rotary body pair capable of holding the recording medium, a drive means for rotatively driving the rotary body, and a moving means for moving the rotary body pair to a first position for conveying the recording medium from a first route to a second route and a second position for conveying the recording medium to other than the above.